Why do Meshes animate weird whenever I do a simple rotation?
I was having this issue earlier. Basically, you need to reset the rotation to zero when you put in the first keyframe. So at frame 0, select the mesh, hit ctrl+a and then select rotation. This is essentially like taring a weight scale. Now press "I" and add locRot. Then go to frame 160, rotate it, and hit "I" then locRot. That should fix it. Make sure you always "tare" the rotation and scale after changing it.

Happy Blendering!